Agile and Prince2

Since Agile doesn’t say much about how to structure a project on a higher level, apart from release planning, it might be interesting to see if and how Agile practices can be combined with for instance a methodology like Prince2. I am going to limit this exercise to Prince2 since I have a certification in and experience with that particular methodology.

Prince2 divides a project in stages. There is the initiation stage, and then you can divide the remainder of the project in as many delivery stages as you see fit, followed by a closing stage.  Prince2 doesn’t say anything about the activities of these stages, except for the initiation stage. In that stage, a project charter, business case, risk register and so on are to be produced. This makes sense in an Agile environment too. You will have a run-up towards the first sprint where you need to define the vision, an initial story map and backlog, provide estimates, establish a fist release planning, do resource allocation, and translate this into a budget that can be included in a business case for approval by senior management. All this qualifies as an initiation stage as defined in Prince2.

During the delivery stages, you can plan whatever you see fit. This means you can take your release planning and consider the various releases of your project as stages in a Prince2 sense. You can create your stage plans as per Prince2 and describe in them the high level scope, risks and a baseline release burn-up or burn-down.  If you need to add teams or change team composition from one release to the next, that too can go in the stage plan. The stage will consist of several Sprints that make up the release. Prince2 mandates that the business case be reviewed after each stage to see if the project still makes sense and that comes very close to Agile practices indeed.

As for the roles, the central figure in Prince2 is the project manager. He has one or more teams working for him each with a team leader. There is no reason why these teams shouldn’t be Scrum teams with a Scrum Master. The project manager then becomes a sort of overall Scrum Master for the project, with all the responsibilities of a project manager in Prince2, as well as supporting the teams and other scrum masters in removing impediments. In Prince2 the users are represented in the Steering Committee by the Senior User. This person could take up the role of the Product Owner, or delegate that to someone in his organization, as long as the delegate has full autonomy and authority to make decisions the correspond to the Product Owner role.

Prince2 is based on a set of principles, that are listed in the table below.

Principle	Definition
Continued business justification	A PRINCE2 project has continued business justification
Learn from experience	PRINCE2 project teams learn from previous experience (lessons are sought, recorded and acted upon throughout the life of the project)
Defined roles and responsibilities	A PRINCE2 project has defined and agreed roles and responsibilities with an organizational structure that engages the business, user and supplier stakeholder interests
Manage by stages	A PRINCE2 project is planned, monitored and controlled on a stage-by-stage basis
Manage by exception	A PRINCE2 project has defined tolerances for each project objective to establish limits of delegated authority
Focus on products	A PRINCE2 project focuses on the definition and delivery of products, in particular their quality requirements
Tailor to suit the project environment	PRINCE2 is tailored to suit the project’s size, environment, complexity, importance, capability and risk

These are compatible with Agile principles and practices like iterative development, the focus on working software, clear definition of roles and empowered teams. As long as the project stays within tolerance for budget and schedule, the teams can proceed in the way that they think is best.

In short, I don’t see any fundamental incompatibilities between Prince2 and Agile. I think the combination of these two can go a long way in addressing senior management concerns on for example development teams doing whatever they want or scope not being fixed up front that you sometimes hear when an organization wants to move to Agile.

Estimating Part III

Sometimes I hear discussions or questions about the reasons for using the Fibonacci scale when estimating in story points. I think the main reason is that the Fibonacci scale jumps in steps of around 50% between the consecutive values. For estimating purposes this is fine, it is much easier to make a distinction between something of size 8 and 13, than between 10 and 11. To make this point more clear, let’s do a thought exercise.

Suppose we are looking at 4 buildings,  a 1 story building, a 2 story building, a 3 story building and a 4 story building. The buildings have flat roofs. The height of the stories in each building is not necessarily the same. The goal is to estimate the sum of the height if the buildings in meters just by looking at it. We will start using a linear scale. 

The 1 story building is probably between 2 and 4 meters high, the 2 story building between 5 and 7 meters, the 3 story building between 8 and 10 and the 4 story building between 10 and 14 meters high. In a table this looks like this:

So we have a minimum total height of 25 meters and a maximum of 35 meters with an average of 30 meters. We could have long discussions on each individual building and come up with any number in this range. Deciding for example whether building 3 is 8 or 9 meters high could be difficult, and any way it wouldn’t make a big difference on the total.

Now let’s do the same exercise using Fibonacci numbers, i.e.  we take the Fibonacci sequence as our possible values for the heights of the buildings. A reasonable estimate for each is then shown in the table below:

2 meters is probably a little low for a 1 story building and 5 too high, so we take 3. The 2 story building is obviously higher than 3 meters, but 8 is likely too much so we take 5 meters. The 3 story building is higher than 5 meters, but 13 meters sounds like too much, so we settle on 8 meters. The 4 story building is likely 13 meters high, since 21 meters is again too high. This gives a total of 29 meters, only 1 meter less than the average we calculated above, and without going into too much detail like the height of the individual floors of the buildings.

So by using Fibonacci numbers we can get to a reasonable estimate pretty quickly, even if we don’t know too much detail yet about the individual buildings and floors in this case. In my previous post I showed a table with the results of a fictional planning poker session using Fibonacci numbers and came to some conclusions about accuracy, precision and confidence. I repeat that table below.

How would that work out if we would replace the Fibonacci scale with a linear scale, i.e. 1, 2, and 3 point user stories stay the same, but a 5 point story becomes a 4 point story, an 8 point story becomes a 5 point story, a 13 point story becomes a 6 point story and so on? Below is the table with the individual estimates converted to a linear scale value.

You see that with the linear scale we get a lower estimate and a higher precision, the 2σ value of 12.14 is 28% of the average of 42.6, whereas with the Fibonacci sequence we had a precision of 53%.

We now repeat this exercise again but with a quadratic scale, i.e. a 1 point story and a 2 point story stay the same, but a 3 point story becomes a 4 point story, a 5 point story becomes an 8 point story, an 8 point story becomes a 16 point story, a 13 point story becomes a 32 point story and so on. The result is in the table below.

We now have a much higher average of 218.8 story points and a 2σ value of 163.29, or 75% of the mean. So with a quadratic scale we get much higher and much less precise estimates when compared to using the Fibonacci scale.

My conclusion is that by using Fibonacci numbers you have a good compromise between accuracy and precision, and it is also easier to use. There is no need for intermediate numbers like maybe one would be tempted to use when using the quadratic scale (and if you do, it would start to converge to the Fibonacci scale anyway). Likewise, there’s no need to skip numbers as you might be tempted to do when using the linear scale (and again, if you do that you converge towards the Fibonacci scale).